Well, I really made a mess with the last commit; this one sorts it out.

src/c/ops/assoc.c

@@ -0,0 +1,92 @@
+/**
+ *  ops/assoc.c
+ *
+ *  Post Scarcity Software Environment: assoc.
+ *
+ *  Search a store for the value associated with a key.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <stdbool.h>
+
+#include "memory/node.h"
+#include "memory/pointer.h"
+#include "memory/pso2.h"
+#include "memory/tags.h"
+
+#include "payloads/cons.h"
+
+#include "ops/eq.h"
+#include "ops/truth.h"
+
+/**
+ * @brief: fundamental search function; only knows about association lists
+ *
+ * @param key a pointer indicating the key to search for;
+ * @param store a pointer indicating the store to search;
+ * @param return_key if a binding is found for `key` in `store`, if true
+ * 			return the key found in the store, else return the value
+ *
+ * @return nil if no binding for `key` is found in `store`; otherwise, if
+ * 			`return_key` is true, return the key from the store; else
+ * 			return the binding.
+ */
+struct pso_pointer search( struct pso_pointer key,
+                                  struct pso_pointer store,
+                                  bool return_key ) {
+	struct pso_pointer result = nil;
+	bool found = false;
+
+	if (consp( store)) {
+		for ( struct pso_pointer cursor = store;
+				consp( store) && found == false;
+				cursor = cdr( cursor)) {
+			struct pso_pointer pair = car( cursor);
+
+			if (consp(pair) && equal(car(pair), key)) {
+				found = true;
+				result = return_key ? car(pair) : cdr( pair);
+			}
+		}
+	}
+
+	return result;
+}
+
+/**
+ * @prief: bootstap layer assoc; only knows about association lists.
+ *
+ * @param key a pointer indicating the key to search for;
+ * @param store a pointer indicating the store to search;
+ *
+ * @return a pointer to the value of the key in the store, or nil if not found
+ */
+struct pso_pointer assoc( struct pso_pointer key, struct pso_pointer store) {
+	return search( key, store, false);
+}
+
+/**
+ * @prief: bootstap layer interned; only knows about association lists.
+ *
+ * @param key a pointer indicating the key to search for;
+ * @param store a pointer indicating the store to search;
+ *
+ * @return a pointer to the copy of the key in the store, or nil if not found.
+ */
+struct pso_pointer interned(struct pso_pointer key, struct pso_pointer store) {
+	return search( key, store, true);
+}
+
+/**
+ * @prief: bootstap layer interned; only knows about association lists.
+ *
+ * @param key a pointer indicating the key to search for;
+ * @param store a pointer indicating the store to search;
+ *
+ * @return `true` if a pointer the key was found in the store..
+ */
+bool internedp(struct pso_pointer key, struct pso_pointer store) {
+	return !nilp( search( key, store, true));
+}

src/c/ops/assoc.h

@@ -0,0 +1,28 @@
+/**
+ *  ops/assoc.h
+ *
+ *  Post Scarcity Software Environment: assoc.
+ *
+ *  Search a store for the value associated with a key.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_ops_assoc_h
+#define __psse_ops_assoc_h
+
+#include <stdbool.h>
+
+#include "memory/pointer.h"
+
+struct cons_pointer search( struct pso_pointer key,
+                                  struct pso_pointer store,
+                                  bool return_key );
+
+struct pso_pointer assoc( struct pso_pointer key, struct pso_pointer store);
+
+struct pso_pointer interned(struct pso_pointer key, struct pso_pointer store);
+
+bool internedp(struct pso_pointer key, struct pso_pointer store);
+#endif

src/c/ops/reverse.c

@@ -0,0 +1,55 @@
+/**
+ *  ops/reverse.c
+ *
+ *  Post Scarcity Software Environment: reverse.
+ *
+ *  Reverse a sequence. Didn'e want to do this in the substrate, but I need
+ *  if for reading atoms!.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#include <stdbool.h>
+
+#include "memory/node.h"
+#include "memory/pointer.h"
+#include "memory/pso.h"
+#include "memory/pso2.h"
+#include "memory/tags.h"
+
+#include "payloads/cons.h"
+#include "payloads/exception.h"
+#include "payloads/psse_string.h"
+
+#include "ops/string_ops.h"
+#include "ops/truth.h"
+
+struct pso_pointer reverse( struct pso_pointer sequence) {
+	struct pso_pointer result = nil;
+
+	for (struct pso_pointer cursor = sequence; !nilp( sequence); cursor = cdr(cursor)) {
+		struct pso2* object = pointer_to_object( cursor);
+		switch (get_tag_value(cursor)) {
+		case CONSTV :
+				result = cons( car(cursor), result);
+				break;
+		case KEYTV :
+			result = make_string_like_thing( object->payload.string.character, result, KEYTAG);
+			break;
+		case STRINGTV :
+			result = make_string_like_thing( object->payload.string.character, result, STRINGTAG);
+			break;
+		case SYMBOLTV :
+			result = make_string_like_thing( object->payload.string.character, result, SYMBOLTAG);
+			break;
+		default :
+			result = make_exception( c_string_to_lisp_string(L"Invalid object in sequence"), nil, nil);
+			goto exit;
+			break;
+		}
+	}
+exit:
+
+	return result;
+}

src/c/ops/reverse.h

@@ -0,0 +1,21 @@
+/**
+ *  ops/reverse.h
+ *
+ *  Post Scarcity Software Environment: reverse.
+ *
+ *  Reverse a sequence.
+ *
+ *  (c) 2026 Simon Brooke <simon@journeyman.cc>
+ *  Licensed under GPL version 2.0, or, at your option, any later version.
+ */
+
+#ifndef __psse_ops_reverse_h
+#define __psse_ops_reverse_h
+
+#include <stdbool.h>
+
+#include "memory/pointer.h"
+
+struct pso_pointer reverse( struct pso_pointer sequence);
+
+#endif